1. Field of the Invention
Some embodiments described herein relate to a transmission apparatus mounted on a vehicle and a method for controlling a transmission apparatus.
2. Description of the Related Art
In related art, various transmission systems have been employed for transmission apparatuses in drive systems of vehicles. One of them is a manual transmission (hereinafter, referred to as “MT”) system for a driver to change the transmission gear using a clutch lever and a change pedal (shift pedal).
Or, an automatic transmission (AT) system of changing transmission gear by automatically driving a shift actuator in response to a vehicle speed, an engine speed, or the like may be used.
As to the AT system, torque converter AT for automatic transmission by combining a torque converter and a planetary gear under hydraulic control is mounted in the largest number of vehicles. In the torque converter AT, times of ratio-change are finely set based on various elements including the degree of pressing the accelerator and the vehicle speed under computer control.
Further, the AT system includes an automated manual transmission (hereinafter, referred to as “AMT”) system of automating only the clutch operation and combining a manually-selected multistage transmission having the same structure as the MT system in the clutch and the gearbox themselves.
The AMT system is also called a semi-automatic transmission system, and only the clutch operation is automatic and the driver performs selection of the throttle and the transmission gears by the operation of the MT system as it is. That is, the shift actuator is driven according to a drivers command and the transmission gear is changed.
Currently, the AMT mounted on a passenger vehicle controls the throttle opening and the actuators of the clutch and the gearbox by fly-by-wire (electronic control) and automatically selects the gear. Further, as a transmission apparatus mounted on an automobile, a dual clutch automated manual transmission (DCT) as an AMT system having two power transmission paths is known.
Furthermore, there is a continuously variable transmission (hereinafter, referred to as “CVT”) system that can steplessly change the transmission ratio in a transmission apparatus from low to top, not changing the gear.
In the CVT, the ratio between the speed of the driving side and the speed of the driven side in the transmission apparatus, i.e., the transmission ratio can be continuously and steplessly changed, and the driver performs only the accelerator operation and the transmission ratio is automatically set according to the driving situations defined by the manipulated amount of the accelerator, the vehicle speed, and drive load.
In the AT system, the AMT system, or the DCT system, the CVT system, generally, compared to the MT system, the clutch operation and the shift operation of setting the transmission ratio are automated, the clutch operation and the shift operation of the driver are eliminated, and thereby, the driving operation is simplified.
Further, in the transmission apparatuses of the AT system, or the AMT system, the DCT system, the CVT system, when the vehicle is turning, delay of ratio-change and restriction of ratio-change are demanded. That is, suppression of unintentional ratio-change by the driver is demanded during turning. Particularly, in a motorcycle, it is necessary to adjust to increase or decrease the output drive force in the rear wheel when turning. Specifically, when the motorcycle turns, the bank angle of the vehicle may be adjusted by the adjustment of increasing or decreasing the drive force, and a preferable turn using the operation is obtained. In this regard, the driver increases or decreases the accelerator to adjust the drive force, and thereby, adjusts the bank angle of the vehicle. While a motorcycle is specifically described herein, the same operations and forces may apply to other two-wheeled vehicles.
When the motorcycle is turning, the transmission ratio of the transmission apparatus may be changed without a drivers intention. Therefore, the output drive force changes regardless of the driver's intention so that controlling the bank angle of the vehicle becomes difficult.
In related art, vehicles may perform a correction based on the rotation speed of the front wheel in the control of a transmission apparatus including a transmission. For example, in International Publication WO2012/067234, whether or not the vehicle is turning is determined using the difference between the vehicle speed calculated from the rotation speed of the front wheel and the vehicle speed calculated from the rotation speed of the rear wheel. If the vehicle is turning, a correction is executed in the in transmission control to delay a ratio-change time and restrict a ratio-change.